React.useRef for functions.

useFunctionRef.js

// Copyright (c) 2021 Wen-Zhi (Alexander) Wang <zxcvb22217@gmail.com>
// SPDX-License-Identifier: MIT

import { useRef } from 'react';

function assert(mayBeFunction) {
  if (typeof mayBeFunction !== 'function' && mayBeFunction != null) {
    console.log(mayBeFunction);
    throw new Error(
      'It is now allowed to pass in a thing that is not a function, ' +
        'undefined, or null to useFunctionRef'
    );
  }
}

/**
 * `React.useRef` for functions.
 *
 * If `undefined` or `null` is passed in, `current` returns a dummy
 * function, so `current` is always callable.
 * @param {function} initialFunction
 * @returns
 */
export function useFunctionRef(initialFunction) {
  assert(initialFunction);
  const r = useRef(
    (() => {
      const dummyFn = () => {};
      let fn = initialFunction || dummyFn;
      return {
        get current() {
          return fn;
        },
        set current(newFn) {
          assert(newFn);
          fn = newFn || dummyFn;
        },
      };
    })()
  );
  return r.current;
}